4. Conclusions

The addition of an organic shrinkage-reducing admixture was observed to have the following effects in the present experiments:

• 1) a significant reduction in the surface tension of a solution containing the SRA relative to distilled water,
• 2) a concurrent increase in the drying rate of bulk solutions,
• 3) a change in the drying profile from uniform drying to a sharp drying front for w/c=0.35 cement pastes exposed to drying conditions,
• 4) a concurrent decrease in the drying rate of cement pastes,
• 5) no influence on the achieved degree of hydration for cement pastes cured under sealed conditions for 11 d,
• 6) a decrease in the internal relative humidity reduction in low w/c ratio cement pastes and mortars cured under sealed conditions,
• 7) a significant decrease in autogenous shrinkage in low w/c ratio mortars cured under sealed conditions, and
• 8) no change or a slight increase in 28 d compressive strength for w/s=0.35 (8 % silica fume) mortar cylinders cured under sealed conditions at 30 ºC.

These results will have implications for the mitigation of early age cracking in low w/c ratio concretes and also possibly for the design of improved curing systems and methodologies.